Jolteon
Umbreon
Espeon
Vaporeon
Glaceon
Leafeon
Flareon
Jolteon is my favorite by far. If you have a Gyarados on your team, it's really easy to get in (Gyarados attracts Electric attacks, Jolteon heals 25% when hit with one due to Volt Absorb). It's extremely fast, and very powerful too.
Umbreon is next just because I really like Dark types. Even if the only way it can really damage things is through Toxic, it can absorb hit after hit after hit.
Espeon has very high special attack and a good movepool to use along with it. It makes a strong sweeper, and it's much easier to switch in than Glaceon (who has only one resistance and a weakness to Stealth Rock).
Vaporeon is next because of its huge HP. It can do an awesome job of healing teammates with Wish, and it can attack with a strong special attack as well.
Glaceon is only ahead of Leafeon because I really like Ice types. It's also way down here because it's an Ice type. It has one resistance in contrast to four weaknesses. Ice is an awesome type for attacks, not for Pokemon.
Leafeon is way down here despite its awesome physical stats because it is completely walled by Steel types, who are very common. Plus, a much better name would have been Vineon.
Flareon is last because its physical movepool just plain sucks. It can run a good mixed attacking set, though.
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